# A question on Elementary Set Theory

In a recent survey of $400$ students in a college, $100$ were listed as studying typing and $150$ were listed as doing accountancy.

a. Find the number of students in the college who are not registered for either course?

b. How many students were registered for typing only?

Illustrate the results with a Venn diagram.

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–  wj32 Oct 24 '12 at 6:11
Hello welcome to MSE. Would you please show your attempts at this question to let us see what you might need? –  FrenzY DT. Oct 24 '12 at 6:12
This question has a short, simple answer: the information given is not sufficient to answer the question. One can illustrate this by giving multiple solutions consistent with the problem statement. Closing it as not constructive is absurd. Closing it as not a real question would have been defensible, if in my view unnecessarily harsh. –  Brian M. Scott Oct 24 '12 at 17:09
There is now a meta question about the closure of this question. –  Bill Dubuque Oct 24 '12 at 18:39
Kenneth, Welcome to math.SE! Please consider taking the time to read the faq to familiarise yourself with some of our common practices. In addition, this page should give you a start at learning how to typeset mathematics here so that your posts say what you want them to, and also look good. As this question appears to be homework, please consider reading this page for information about asking effective homework-related questions. And showing your work will make people more likely to help. –  mixedmath Oct 24 '12 at 21:10

## 1 Answer

Like your first question, this one has no definite answer, because it doesn’t contain enough information. From what we’re told, it’s possible that all of the students who were taking typing were also taking accountancy; in that case there would be $400-150=250$ students not registered for either course, and no students registered for typing only. At the other extreme it’s possible that no student is taking both typing and accountancy; in that case there are $$400-(100+150)=400-250=150$$ students who are not registered for either course, and $100$ who are registered for typing only.

Where are you finding these questions? Are you sure that you’re giving us all of the information in the questions? Questions of this type usually do have enough information, so either you have a very odd source, or you’re missing something when you interpret the questions.

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I can't help but wonder if there is some sort of picture/image associated with these questions. –  The Chaz 2.0 Oct 25 '12 at 14:21
@TheChaz: Might be, although the part about making a Venn diagram seems to suggest otherwise. –  Brian M. Scott Oct 25 '12 at 14:26